Determinants of Hypercapnia in Obese Patients With Obstructive Sleep Apnea: A Systematic Review and Metaanalysis of Cohort Studies

摘要

Background: Inconsistent information exists about factors associated with daytime hypercapnia innobese patients with obstructive sleep apnea (OSA). We systematically evaluated these factors innthis population.nMethods: We included studies evaluating the association between clinical and physiologicnvariables and daytime hypercapnia (PaCO2, > 45 mm Hg) in obese patients (body mass indexn[BMI], > 30 kg/m2n) with OSA (apnea-hypopnea index [AHI], > 5) and with a < 15% prevalencenof COPD. Two investigators conducted independent literature searches using Medline, Web ofnScience, and Scopus until July 31, 2008. The association between individual factors andnhypercapnia was expressed as the mean difference (MD). Random effects models were used tonaccount for heterogeneity.nResults: Fifteen studies (n u0001 4,250) fulfilled the selection criteria. Daytime hypercapnia wasnpresent in 788 patients (19%). Age and gender were not associated with hypercapnia. Patientsnwith hypercapnia had higher BMI (MD, 3.1 kg/m2n; 95% confidence interval [CI], 1.9 to 4.4) andnAHI (MD, 12.5; 95% CI, 6.6 to 18.4) than eucapnic patients. Patients with hypercapnia had lowernpercent predicted FEV1 (MD, u000211.2; 95% CI, u000215.7 to u00026.8), lower percent predicted vitalncapacity (MD, u00028.1; 95% CI, u000211.3 to u00024.9), and lower percent predicted total lung capacityn(MD, u00026.4; 95% CI, u000210.0 to u00022.7). FEV1/FVC percent predicted was not different betweennhypercapnic and eucapnic patients (MD, u00021.7; 95% CI, u00024.1 to 0.8), but mean overnight pulsenoximetric saturation was significantly lower in hypercapnic patients (MD, u00024.9; 95% CI, u00027.0nto u00022.7).nConclusions: In obese patients with OSA and mostly without COPD, daytime hypercapnia wasnassociated with severity of OSA, higher BMI levels, and degree of restrictive chest wallnmechanics. A high index of suspicion should be maintained in patients with these factors, asnearly recognition and appropriate treatment can improve outcomes.